HTML5 is moving to an unversioned model

It means that from now on the technology is not versioned and instead WhatWG just has a living document that defines the technology as it evolves.

Because the specification is now a living document, we are today announcing two changes:

The HTML specification will henceforth just be known as "HTML", with the URLhttp://whatwg.org/html. (We will also continue to maintain the Web Applications 1.0 specification that contains HTML and a number of related APIs like Web Storage, Web Workers, and Server-Sent Events.)

The WHATWG HTML spec can now be considered a "living standard". It's more mature than any version of the HTML specification to date, so it made no sense for us to keep referring to it as merely a draft. We will no longer be following the "snapshot" model of spec development, with the occasional "call for comments", "call for implementations", and so forth.